Cross-flow film cooling passages

Abstract

Film coolant passages through the wall of a hollow airfoil for a gas turbine engine are oriented to direct coolant fluid therefrom at a substantial acute angle to the downstream direction and at a shallow angle to the surface of the airfoil. Each passage includes a metering portion at its inlet end and a four sided diffusing portion at its outlet end. The diffusing portion includes a pair of adjoining surfaces which are both parallel to a central axis of the passage, and another pair of adjoining surfaces which diverge from the central axis, the diverging pair of surfaces being located on the downstream side of the passage. With this configuration the coolant completely fills the diffusing section and exits as a wide film of coolant within the boundary layer downstream of the passage outlet.

I claim: 
     
       1. A cooled wall having an outer surface adapted to be exposed to a hot gas stream flowing in a downstream direction over said outer surface, and an inner surface adapted to define a portion of a coolant compartment for receiving coolant therein under pressure, the improvement comprising: a coolant passage within said wall, said passage including a metering section and a diffusing section in series flow relation, said metering section having an inlet adapted to receive a flow of coolant from the coolant compartment and adapted to control the rate of flow of coolant fluid through said passage, said metering section including a straight portion having a central axis, said central axis forming a shallow angle with said outer surface of said wall and forming a projected angle of between 20° and 90° with the downstream direction in a plane substantially tangent to said outer surface at said coolant passage outlet, said diffusing section including an upstream side surface parallel to the central axis and a downstream side surface spaced from and facing said upstream side surface and diverging from said upstream side surface toward said passage outlet at a first angle, said diffusing section also including an upstream end surface parallel to the central axis and a downstream end surface spaced from and facing said upstream end surface and diverging from said upstream end surface toward said passage outlet at a second angle, said upstream and downstream end surfaces interconnecting said upstream and downstream side surfaces, said side surfaces and end surfaces intersecting said outer surface to define said passage outlet.   
     
     
       2. The cooled wall according to claim 1 wherein said second angle is between 5° and 15°. 
     
     
       3. The cooled wall according to claim 2 wherein said first angle is between 5° and 15°. 
     
     
       4. The cooled wall according to claim 3 wherein said projected angle is between 40° and 70°. 
     
     
       5. The cooled wall according to claim 3 wherein said shallow angle is less than about 30°. 
     
     
       6. The cooled wall according to claim 5 wherein said projected angle is between 40° and 70°. 
     
     
       7. The cooled wall according to claim 1 wherein said straight portion of said metering section intersects said inner surface to form an inlet to said coolant passage, and said straight portion comprises an outlet which is also an inlet for said diffusing section. 
     
     
       8. The cooled wall according to claim 7 wherein said straight portion of said metering section includes a first surface extending the length of said straight portion and which is in the same plane as said upstream end surface, and wherein said straight portion of said metering section includes a second surface extending the length of said straight portion and which is in the same plane as said upstream side surface. 
     
     
       9. The cooled wall according to claim 1 wherein said wall is the external wall of a hollow airfoil. 
     
     
       10. The cooled wall according to claim 4 wherein said wall is the external wall of a hollow airfoil. 
     
     
       11. The cooled airfoil wall according to claim 10 wherein said shallow angle is less than about 30°. 
     
     
       12. The cooled airfoil wall according to claim 10 wherein said straight portion of said metering section includes a first surface extending the length of said straight portion and which is in the same plane as said upstream end surface, and wherein said straight portion of said metering section includes a second surface extending the length of said straight portion and which is in the same plane as said upstream side surface. 
     
     
       13. The cooled wall according to claim 8 wherein said wall is the external wall of a hollow airfoil. 
     
     
       14. The cooled airfoil wall according to claim 12 including a plurality of said coolant passages therethrough having their outlets spaced apart and substantially aligned in the spanwise direction of said airfoil wall. 
     
     
       15. The cooled airfoil wall according to claim 12 wherein said projected angle is about 45°.